1. Field of the Invention
The present invention relates to radar and communication systems. More specifically, the present invention relates to radar and communication systems that are adapted to circumvent interference.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Conventional radar systems operate over a narrow band at a single carrier frequency. As a result, these systems were susceptible to interference. Many schemes have been developed to address this problem, two of which are the frequency hopping and spread spectrum schemes. Frequency hopping involves the transmission of a block of data at one carrier frequency, then "hopping" to another carrier frequency and transmitting another block of data and so on.
Unfortunately, when frequency hopping is employed, it is difficult, if not impossible to coherently add individual pulses together to improve the signal-to-noise ratio. While slow hopping may preserve the (phase) coherency of the pulses, slow hopping is considerably more susceptible to interference.
Conventional spread spectrum systems operate at a single carrier over a wide bandwidth. However, these systems create many intermodulation products. Thus, a considerable amount of power may be wasted in spurious sidebands. In addition, the coherency of the signals is uncertain.
Further, neither the conventional frequency hopping schemes nor the conventional spread spectrum schemes fully exploit the wide bandwidth capabilities of current traveling wave tube amplifiers.
Thus, a need exists in the art for a radar transmitter which is secure from interference, offers the performance advantages of phase coherency, is power efficient and is capable of taking advantage of the broad bandwidth of current traveling wave tube amplifiers.